a students average test score on 4 tests is 78.what must be the students scoe on 5th test for the students avg score on the 5th test to be 80

The selling price of 13 apples is the same as the cost price of 26 mangoes . The selling price of 16 mangoes is the same as the cost price of 12 apples. If the profit on selling mangoes is 20%, What is the profit on selling apples?